Abstract
The 26mAl(p,γ)27Si reaction is thought have a significant impact of the nucleosynthesis of both 26Mg and 27Al in explosive stellar environments, where T > 0.3 GK. The isomeric component of 26Al forms part of the T = 1, isospin triplet 26Si-26mAl-26Mg. As such, the 26Si(d,p)
27Si transfer acts as a novel surrogate reaction that populates the final states within 27Si. No γ-ray transitions were observed for proton-unbound states, suggesting the no strong single-particle states within the energy range Er = 100 - 500 keV. Stellar reaction rate upper limits were placed on known resonances at 146, 218, 378, 448 and 492 keV, based on excess counts observed within respective γ-ray transition energy regions. These indicate that a single resonance dominates the reaction rate at a given temperature, the 218 keV resonance at T < 0.3 GK and the 448 keV resonance at T > 0.3 GK. Most importantly these reaction rates are much smaller than previously estimated.
The 22Ne(α,γ) 26Mg reaction is a n-poison reaction within the weak s-process of massive stars. It is thought that the reaction rate will be dominated by resonant capture to natural-parity excited states between the α-emission and n-emission thresholds within 26Mg, at energies of 10614.75 keV and 11093.09 keV respectively. The indirect reaction 25Mg(d,p)26Mg was performed to investigate possible γ-ray decaying state above these thresholds. No states above the n-emission threshold was observed, suggesting that there are no strong γ-ray decaying single-particle states in this system. Mirror analogue states for the astrophysical 25Al(p,γ) 26Mg resonant-capture reaction were analysed, extracted spectroscopic factors were compared to shell-model calculations and literature values. Of note was the re-assertion of a possible low-lying negative parity state, with energy of 5.710 MeV, within the 26Mg system as noted by previous (d,p) transfer reaction studies. Whilst no measurements of this state could be made within this study the need for further study was re-affirmed.